2 different MX records at same priority?

walesrob · 1 Feb 2008, 07:16 AM

The correct standard is to have MX records in lower to higher value, i.e. mx1 :10 and mx2: 20, but is it acceptable to have 2 seperate MX servers on same priority, ie.

mx.provider1.com 10
mx.provider2.com 10

Does this ensure proper distribution of email if provider1 goes down?

Thanks in advance for any answers!

janusz · 1 Feb 2008, 06:59 PM

yes, that's perfectly acceptable. This method is used, for example, to distribute the load over a number of servers (used in a round robin manner)

Scott Kitterman · 8 Feb 2008, 01:41 AM

It does not, however, give you increased reliability. If the primary MX is down, properly designed mail servers will try lower priority MX records, so more at the same priority doesn't help.

janusz · 8 Feb 2008, 04:24 AM

Properly designed mail server, faced with a number of MX records of equal priority, should try one record first (doesn't matter which) and if it gets no response, try other(s) in turn in some sort of order.

tuntun · 26 Feb 2008, 10:27 AM

I did try this morning on office DNS. I found mails dealy and some got bounced. Any solutions? After set priority with different level, mails are OK.

walesrob · 29 Feb 2008, 06:39 PM

Quote:

Originally Posted by Scott Kitterman

It does not, however, give you increased reliability. If the primary MX is down, properly designed mail servers will try lower priority MX records, so more at the same priority doesn't help.

Thanks Scott, I'll stick to the tried and tested.

Also, I'm still a bit confused about using periods (.) after mx records, so if my domain:

10 mail.thatprovider.com
20 mxes.thisprovider.net

Would it be technically correct to put periods after each entry or after the last entry?

wdunn mailtrust · 29 Feb 2008, 09:18 PM

Quote:

Originally Posted by walesrob

Thanks Scott, I'll stick to the tried and tested.

Also, I'm still a bit confused about using periods (.) after mx records, so if my domain:

10 mail.thatprovider.com
20 mxes.thisprovider.net

Would it be technically correct to put periods after each entry or after the last entry?

In practice, this totally depends on the registrar where you edit your DNS entries, and how sophisticated their control panel is.

In an actual bind/named zone file, they have to have the trailing period, IIRC. (see http://www.redhat.com/docs/manuals/l...bind-zone.html)

But I've seen registrar control panels where it just regex's out the period if you put one to normalize input and adds it on the backend.

I dunno, it's something about FQDN's and high level DNS stuff, I believe it's because technically the trailing dot represents the root level of DNS search. It means you can read it backwards and get the correct authoritative nameserver for each part, i.e. some-server.some-domain.com. when split and read backwards becomes ".com", then ".some-domain", then ".some-server". I have no idea why this is optimal, but the need to read things backwards explains a lot about DNS, imo.

~W

George_B · 3 Mar 2008, 09:29 PM

The only thing I might add is that if your provider tells you which one is primary and which is secondary/third and so on, that you follow that order.

For example, our primary MX is the incoming mail array and the 2nd MX is a simple store and forward server in case of outage of the first MX.

If you set them both on equal priority, you may find that some e-mails arrive slightly slower.

1 Feb 2008, 07:16 AM	#1
walesrob Essential Contributor Join Date: Dec 2006 Location: UK Posts: 392	2 different MX records at same priority? The correct standard is to have MX records in lower to higher value, i.e. mx1 :10 and mx2: 20, but is it acceptable to have 2 seperate MX servers on same priority, ie. mx.provider1.com 10 mx.provider2.com 10 Does this ensure proper distribution of email if provider1 goes down? Thanks in advance for any answers!

26 Feb 2008, 10:27 AM	#5
tuntun Junior Member Join Date: Feb 2008 Posts: 25	MX Records I did try this morning on office DNS. I found mails dealy and some got bounced. Any solutions? After set priority with different level, mails are OK.

1 Feb 2008, 06:59 PM	#2
janusz Intergalactic Postmaster Join Date: Feb 2006 Location: EU Posts: 5,002	yes, that's perfectly acceptable. This method is used, for example, to distribute the load over a number of servers (used in a round robin manner)

8 Feb 2008, 01:41 AM	#3
Scott Kitterman Essential Contributor Join Date: Sep 2006 Location: Ellicott City, MD, USA Posts: 206 Representative of: ControlledMail.com	It does not, however, give you increased reliability. If the primary MX is down, properly designed mail servers will try lower priority MX records, so more at the same priority doesn't help.

8 Feb 2008, 04:24 AM	#4
janusz Intergalactic Postmaster Join Date: Feb 2006 Location: EU Posts: 5,002	Properly designed mail server, faced with a number of MX records of equal priority, should try one record first (doesn't matter which) and if it gets no response, try other(s) in turn in some sort of order.

3 Mar 2008, 09:29 PM	#8
George_B Cornerstone of the Community Join Date: Jan 2008 Posts: 709 Representative of: PolarisMail.com	The only thing I might add is that if your provider tells you which one is primary and which is secondary/third and so on, that you follow that order. For example, our primary MX is the incoming mail array and the 2nd MX is a simple store and forward server in case of outage of the first MX. If you set them both on equal priority, you may find that some e-mails arrive slightly slower.